169920

Appears in sequences

• A unitary phi reciprocal amicable number: consider two different numbers r, s which satisfy the following equation for some integer k: uphi(r) = uphi(s) = (1/k) * r * s / (r-s); or equivalently, 1/uphi(r) = 1/uphi(s) = k * (1/s - 1/r); sequence gives s numbers.at n=23A080767
• Number of (n+1) X 5 0..1 arrays with the number of rightwards and downwards edge increases in each 2 X 2 subblock equal to the number in all its horizontal and vertical neighbors.at n=24A206263
• Number of (n+1) X (1+1) 0..3 arrays with every 2 X 2 subblock having the sum of the squares of all six edge and diagonal differences equal to 11.at n=6A233785
• Number of (n+1) X (7+1) 0..3 arrays with every 2 X 2 subblock having the sum of the squares of all six edge and diagonal differences equal to 11.at n=0A233791
• T(n,k)=Number of (n+1)X(k+1) 0..3 arrays with every 2X2 subblock having the sum of the squares of all six edge and diagonal differences equal to 11 (11 maximizes T(1,1)).at n=21A233792
• T(n,k)=Number of (n+1)X(k+1) 0..3 arrays with every 2X2 subblock having the sum of the squares of all six edge and diagonal differences equal to 11 (11 maximizes T(1,1)).at n=27A233792
• Expansion of ((Product_{n>=1} (1 - x^(3*n))/(1 - x^n)^3) - 1)/3 in powers of x.at n=22A277968
• Triangle read by rows: T(n,k) is the number of permutations pi of [n] such that pi has k+1 valleys and s(pi) avoids the patterns 132 and 321, where s is West's stack-sorting map (0 <= k <= floor((n-1)/2)).at n=33A319030
• Triangle read by rows: T(n,k) is the number of patterns of length n with all distinct runs and maximum value k.at n=51A351640